Amate-dicarboxylate-thickened grease



AMATE-DICARBOXYLATE-THICKENED GREASE Joseph A. Dixon, Berkeley, Calif, assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application August 19, 1952, Serial No. 305,288

6 Claims. (Cl. 25233.6)

This patent application is directed to new greasethickening agents for high temperature grease compositions; that is, high temperature grease compositions thickened with amic acid salt-dibasic acid salt mixtures.

It is becoming more and more apparent that, for the most part, greases must be able to lubricate effectively under conditions of high temperatures, that is, temperatures considerably in excess of 400 F., and, in certain instances, in the range of 500 F. Numerous military and industrial grease specifications describe greases having dropping points of 400 F. as a minimum. This need for high temperature greases is the result of increased speeds of gears, bearings, and other moving parts; increased pressures caused by the development of smaller gears to withstand greater loads than heretofore expected of larger gears, etc.

In the automotive industry, for example, there is the constant desire to manufacture smaller internal combustion engines without sacrificing power output. In fact,

nited States Patent many of these smaller engines are designed to deliver greater power than their larger counterparts. The same smaller engines have considerably less'bearing surfaces than the larger predecessors, which means that thebearings gear greater loads than before.

Similarly, the continuing trend to manufacture automobiles with lower centers of gravity has made it necessary to use smaller gears, particularly in such gear assemblies as the differentials and transmissions. The smaller gears thus used have considerably greater pressures ex erted upon them per unit area than the older type gear assemblies. Thus, machines having higher loads on bearings and gears along with greater speeds, require grease compositions which will function at higher temperatures than heretofore necessary.

Greases prepared according to the present invention will maintain grease consistencies at extremely high temperatures; that is, such greases will remain unctuous and not become hard or brittle at such high temperatures in the range of 500 F. Such greases also have excellent resistance to emulsion in water and have excellent antiwear properties.

Certain amic acid salts of themselves thicken lubricating oils to the consistency of greases. Such amic acid salt thickening agents have been prepared from amic acids obtained by reacting stoichiometric amounts of amines and dibasic acids; that is, 1 mole of a primary amine (e. g., lauryl amine) was reacted with 1 mole of a dibasic acid (e. g., sebacic acid) to form the desired amic acid (e. g., N-monolaurylsebacamic acid). This amic acid was then reacted with a metal hydroxide (e. g., sodium hydroxide) to form the sodium soap of the amic acid (e. g., N-lauryl-sodium sebacamate) which was used as a grease thickening agent. Such amic acid salts of themselves are used in the preparation of greases having dropping points in the region of 400 F. However, they are ineffective in the preparation of greases having dropping points in the region of" 500 F.

Dibasic acid salts (e. g., sodiumsebacate) 'of themice selves exhibit no gelation effect when heated in lubricating oils. That is, whendibasic acid soaps are mixed with lubricating oils, and such mixtures are heated to high temperatures (e. g., 500 F.), cooled, and milled, no gel structure nor grease is obtained.

However, it has been discovered that greases having extremely high dropping points, i. e., dropping points in the region of 500 F., can be obtained by the use of grease thickening agents set forth according to the present invention. These new high-temperature grease thickening agents comprise mixtures of amic acid salts and dicarboxylic acid salts. Thus, the grease compositions of the present invention comprise lubricating oils thickened with amic acid salt-dibasic acid salt mixtures.

The amic acid salt-dibasic acid salt mixtures of this invention are prepared by reacting 1 mol of a primary (or secondary) amine with at least 1.5 mols of a dibasic acid to form an amic acid-dibasic acid mixture; which mixture is then reacted with a metal oxide or hydroxide, resulting in an amic acid salt-dibasic acid salt mixture of the present invention.

The amic acid salts which are present in the grease thickening composition described herein are represented by the following formula wherein R is a saturated or unsaturated, straight-chained,

branch-chained or cyclic essentially hydrocarbonaceous radical having from 2 to 50 carbon atoms (8 to 20 preferred), R1 is a saturated or unsaturated straight-chained, branch-chained, or cyclic essentially hydrocarbonaceous radical having from 1 to- 54 carbon atoms, M is a metal, and x is a number having a value equal to the valence of the metal M.

It is preferred that R be a straight-chained or cyclic essentially hydrocarbonaceous radical and that R1 be a straight-chained essentially hydrocarbonaceous radical.

Examples of the R radicals include the following: ethyl, propyl, propenyl, butyl, butenyl, pentyl, hexyl, hexenyl, octyl, octenyl, nonyl, decyl, decenyl dodecyl dodecenyl, tetradecyl, tetradecenyl, hexadecyl, octadecyl, octadecenyl, eicosyl, triacontyl radicals, radicals derived from petroleum hydrocarbons, such as white oil, wax,

olefin polymers, e. g., polypropylene and polybutene, etc.

Examples of R radicals include the following: methylene radicals, i. e., (CI-I2)x, wherein x is a number from 1 to 52 (6 to 24 preferred; 12 to 18 especially preferred) (including methylene radicals which may have one or more saturated or unsaturated, straight-chained, branch- I chained, or cyclic essentially hydrocarbonaceous radical attached'thereto) a phenyl radical; a substituted phenyl radical (wherein the phenyl nucleus contains one or more aliphatic radicals attached thereto); etc.

By essentially hydrocarbonaceous radicals is meant those radicals which are composed mainly of hydrogen and carbonand include such radicals which include, in addition, minor amounts of the substituents such as chlorine, bromine, oxygen, nitrogen, etc.

The dibasic acid salts present in the grease thickening mixtures of the present invention include those represented by the following formula:

wherein M represents a metal, x is a number having a value equal to the valence of the metal, and R2 is a saturated or unsaturated, straight-chained, branch-chained or cyclic essentially hydrocarbonaceous radical; for ex ample, a methylene radical, i. e., (CH2)x, wherein x is a number from 1 to 52 (4 to 16 preferred; 4 to 10 especially preferred) (including such methylene groups which may have one or more saturated or unsaturated, straight-chained, branch-chained or cyclic essentially hydrocarbonaceous radicals attached thereto); a phenyl group; a substituted phenyl radical (wherein the phenyl nucleus has one or more aliphatic radicals attached thereto); etc.

For sake of brevity, the amic acid salts will hereinafter be termed am-ates, and the dibasic acid salts will be termed dicarboxylates.

The metals which can be used in the formation of the soaps of this invention include the metals of groups I, II, III, and IV of Mendeleffs Periodic Table. Particular metals include lithium, sodium, potassium, silver magnesium, calcium, Zinc, strontium, cadmium, barium, aluminum and lead.

Lubricating oils which are suitable base oils for the grease compositions of this invention include a wide variety of lubricating oils, such as naphthenic base, paraffin base, and mixed base, other hydrocarbon lubricants, e. g. lubricating oils derived from coal products, and synthetic oils, e. g., alkylene polymers (such as polymers of propylene, butylene, etc., and mixtures thereof), alkylene oxide type polymers, dicarboxylic acid esters, liquid esters of acids of phosphorus, alkyl benzene polmers, polymers of silicon, etc. Synthetic oils of the alkylene oxide type polymers which may be used include those exemplified by the alkylene oxide polymers (e. g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing the alkylene oxides, e. g., propylene oxide, in the presence of water or alcohols, e. g., ethyl alcohol; esters of ethylene oxide type polymers, e. g., acetylated propylene oxide polymers prepared by acetylating propylene oxide polymers containing hydroxyl groups; polyethers prepared from the alkaline glycols, e. g., ethylene glycol, etc.

The polymeric products prepared from the various alkylene oxides and alkylene glycols may be polyoxyalkylenediols or polyalkylene glycol derivatives; that is, the terminal hydroxy group can remain as such, or one or both of the terminal hydroxyl groups can be removed during the polymerization reaction by esterification or etherification.

Synthetic oils of the dicarboxylic acid ester type include those which are prepared by esterifying such dicarboxylic acids as adipic acid, azaleic acid, suberic acid, sebacic acid, alkenyl succinic acid, fumaric acid, maleic acid, etc. with alcohols such as butyl alcohol, hexyl alcohol, 2-ethyl-hexyl alcohol, dodecyl alcohol, etc. Examples of dicarboxylic acid ester synthetic oils include dibutyl adipate, dihexyl adipate, di-Z-ethylhexyl sebacate, di-n-hexyl fumaric polymer.

Synthetic oils of the alkyl benzene type include those which are prepared by alkylating benzene (e. g., dodecyl benzene, tetradecyl benzene, etc.).

Synthetic oils of the type of liquid esters of acids of phosphorus include the esters of phosphoric acid, e. g., tricresyl phosphate; the esters of phosphonic acid, e. g., the diethyl ester of decanephosphonic acid, etc.

Synthetic oils of the type of polymers of silicon include the liquid esters of silicon and the polysiloxanes. The liquid esters of silicon and the polysiloxanes include those exemplified by tetraethylsilicate, tetraisopropyl silicate, tetra (methyl-Z-butyl) silicate, tetra (4-methyl-2-penta) silicate, tetra (l-methoxy-Z-propyl) silicate, hexyl (4- methyl 2 pentoxy) disiloxane, poly(methylsiloxane), poly(methylphenylsiloxane), etc.

The above base oils may be used individually as such, or in various combinations, wherever miscible or wherever made so by the use of mutual solvents.

Examples of primary amines useful in the preparation of the thickening agents herein include ethylamine, propylamine, butaylamine, butenylamine, pentylamine, octylamine, octenylamine, decylamine, dodecylamine, hexadecylamine, octadecylamine, octadecenylamine, eicosylamine, triacontylamine, etc. The amines may be used individually as such or as mixtures of amines.

Mixtures of amines used in the preparation of the thickening agents of this invention also include mixtures containing minor amounts (less than 50%) of secondary amines.

Examples of dicarboxylic acids include malonic acid, isosuccinic acid, methyl succinic acid, glutaric acid, adipic; acid, pimelic acid, suberic acid, sebacic acid, dicarboxylic acids prepared by polymerizing unsaturated monobasic acids and derivatives (e. g., heating the methyl esters of linoleic acid to form a dilinoleic acid), etc. The dicarboxylic acids may be used either individually as such or as mixtures.

In the preparation of certain grease thickening agents; herein, dicarboxylic acids were used which had been prepared by polymerizing unsaturated monobasic acids. These dicarboxylic acid preparations are known as Dimer acids, and they are obtained from Emery Industries, Inc., Cincinnati, Ohio. These dicarboxylic acid preparations contain a small amount of tricarboxylic acids (approximately 12%), which also form grease-thickening agents when reacted with primary amines, followed by reaction with a metal oxide or hydroxide to form the amatedicarboxylate-tricarboxylate grease-thickening agent.

As noted hereinabove, the amate-dicarboxylate mixture thickening agents of this invention are prepared by first reacting a primary amine with a dibasic acid in such proportions that the mol ratio of the dibasic acid to the amine has a value from 1.5 to 5.0, preferably from 2 to 4. This reaction produces a mixture of amic acids and unreacted dibasic acids, which mixture is then reacted with a metal oxide or hydroxide to form the desired mixture of amates and dicarboxylates.

Although diamides of themselves do thicken lubricating oils to the consistence of greases, it is known that such greases are of relatively low dropping point, that is, in general, in the region of 250 F. The presence of diamides in the grease thickening mixture of the present invention is detrimental to the dropping point.

The amate-dicarboxylate mixtures may be used in the preparation of greases according to this invention in amounts of 6% to 50% by weight, preferably 10% to 30%.

Examples of the greases prepared from the salt mixtures of the present invention are presented as follows:

Example I.Preparati0n of lithium-N-hexaa'ecyl adipamzzte-lithium adipate thickened grease A mixture of 58.5 grams (0.4 mol) of adipic acid and 500 ml. of 95% ethanol was heated to boiling in a 4 liter stainless steel beaker. To this mixture was added 72 grams (0.3 mol) of n-hexadecyl amine (Armeen 16D from Armour & Company) in 200 ml. of ethanol. The ethanol solution of n-primary hexadecyl amine was added dropwise with rapid stirring while the whole reaction mixture was heated at reflux temperature. After all of the n-hexadecyl amine had been added, the ethanol was removed by evaporation.

The resulting solid reaction product was purified by heating the solid product to a temperature of 450 F., then pouring it directly into 1 /2 liters of water with rapid stirring, after which the slurry was heated to the boiling point of water, with stirring. After the slurry had been cooled to F., the solid was removed by filtration, then dried. This dried product was finely ground, dissolved in 500 ml. of boiling benzene, crystallized overnight, filtered and dried.

15 grams of this reaction mixture were dissolved in grams of a California solvent-refined naphthenic base oil having a viscosity of 450 SSU at F. The mixture was stirred and heated at 200 F., at which temperature 1.6 grams of lithium hydroxide monohydrate in 25 ml. of water was added. The whole composition was heated to 400 F., poured into a stainless steel pan to cool, then 'decylamine and octadecenylamine.

Example 2.Preparati0n of grease thickened with lithium- N-hexadecyl dilinoleamide-lithium .dilinoleate 300 grams (1.5 moles) of dilinoleic acid were heated to-300 F., after which 136 grams (0.5 mole) or Armeen HTD were added dropwise during a period of '15 minutes. The reaction mixture was heated, with stirring, at a temperature range of 400 F. to 420F. until all of the water of reaction had been removed. Upon cooling, the

reaction productwas a dark sticky solid having a'neutralization number of 64.

A mixture of gramsof the above solid reaction product and 85 grams of a California solvent-refined naphthenic base oil having a viscosity of 450 SSU .at 100 F. was charged to an 800 ml. Pyrex beaker. was heated, with stirring, to 200 F.,.then anaqueous solution of 1.44 grams of LiOH-HzO wasaadded. The mixture was heated to a temperature of 390 F. After cooling, the product was a clear amber grease.

In the above examples of the grease preparations, the salts were prepared in situ; however, the salts may also be prepared as separate products, then dispersed in oils to form greases. The amic acids themselves may also be prepared directly in the oil.

Table I hereinbelow presents data on the use of amatedicarboxylate mixtures as grease 'thickeners according to this invention. The thickening agents were prepared by reacting various primary amines with adipic acid, followed by reaction with a metal hydroxide. With the exception of greases 9 and 10, which respectively contained 24% and 14%, all of the greases contained 16%, by weight, of the thickening agent.

The various symbols used in Table I are explained as follows:

HTD refers to Armeen HTD, a product of Armour and Company, Chicago, Illinois, containing n-hexadecylamine, 70% n-octadecylamine, and 5% n-octadecenylamine.

T refers to Armeen T, a product of Armour and Company, Chicago, Illinois, containing a mixture comprising hexadecylamine, 25% octadecylaminc and 45% hexadecylamine. 85% of this mixture consists of n-primary amines.

C amine refers to Armeen C, which contains 8% octylamine, 9% decylamine, 47% dodecylamine, 18% tetradecylamine, 8% hexadecylamine, 5% octadecylamine, and 5% octadecenylamine.

TD refers to Armeen TD, which is a purified product of the above Armeen T. The TD product contains 30% n-primary hexadecylamine, 25% n-primary octadecylamine and 45% n-primary octadecenylamine.

HT refers to Armeen HT, which is a mixture of amines comprising 25 hexadecylamine, 70% octa- 85% of this mixture consists of n-primary amines.

Base oil A was a California solvent-refined naphthenic base oil having a viscosity of 450 SSU at 100 F.

Base oil B was a California solventrefined paraffinic base oil having a viscosity of 480 SSU at 100 F.

Base oil C wasa di(2-ethylhexyl) sebacate.

Base oil D was a poly(methylphenyl) siloxane.

Base oil E was a California solvent-refined naphthenic base having a viscosity of 90 SSU at 210 F.

1 This dilinoleic acid is essentially a dibasic acid of approximately 600 molecular weight of Emery Industries, Inc., Cincinnati, Ohio. It is prepared by the dimerization of linoleic acid. Although the product is essentially a dibasic acidv approximately 12% of trilinoleic acid (a tribasic acid) and 3% of linoleic acid (a monobasic acid) are present.

Armeen HTD is a product of the Armour Company, Chicago, Illinois, and contains 25% of n-hexadecylamme, 70% of n-octyldecylamine, and 5% of n-octadecenylamine. The mean molecular weight of this product is 264.

This mixture TABLE I Reactants iotr1 Soap Prepara- Grease Properties Experiment No. Mole Metal Dropping ASTM n-primary Acid/ Hydrox- Point, Penetrate Base amine Mole ide F. (Worked Oil Amine 78 F.)

' hexy1 2 Li 421 360 A cyclohexyl 4 Li 500+ 355 A TD..-" 2 Na 486 B HTD 2 A1 431 304 A phenyL..- 4 Li A octadecyL- 2 Li 474 350 D 2 Li 500+ 284 A 2 L1 500+ 360 A 2 L1 500+ 282 B HT 2 Li 500+ 285 E T 2 Li 500+ 334 A C 3 Li 500+ 313 A When the amate-dicarboxylate grease thickening agents described herein are prepared from high molecular weight amines and/ or high molecular weight dibasic acids, small amounts (e. g.,'less than 6%) of such amate-dicarboxylate excellent lubricating oil thickening agents are obtained;

that is, lubricating oils thickened to the consistency of extremely soft greases or greases having extremely low yield values. Such thickened lubricating oils may be used for filter elements, such as in air filter elements of diesel engines, air-conditioning units in general, etc.

As another embodiment of this invention, a dibasic acid salt may be added to an oil containing an amic acid salt; or a dibasic acid may be mixed with an amic acid before neutralization with a metal. For example, if in the original preparation of the amic acid-dibasic acid mixture, the mole ratio of dibasic acid to amine has a value of l or less than 1, additional dibasic acid may be incorporated into the amic acid thus prepared before neutralization with metal hydroxide, or additional dibasic acid salt may be incorporated into the oil prior to the grease preparation. The dibasic acid (or salt) added may or may not be the same as that used in the original preparation.

The necessity for the presence of dibasic acid salts in the grease thickening agents of this invention is illustrated in Example 3 hereinbelow.

Example 3 An amic acid-dibasic acid mixture (product A) was prepared from 219 grams (1.5 mols) of adipic acid and 311 grams (1 mol) of Armeen T (defined hereinabove). A portion of this mixture (which contained 2.68% nitrogen) was saponified with lithium hydroxide monohydrate and dispersed in a California solvent-refined oil, forming a grease having a dropping point of 435 F.

A second portion of the above amic acid-dibasic acid mixture was thoroughly agitated in hot water, separating the adipic acid from the amic acid. The amic acid (product B) contained 3.04% nitrogen. This amic acid was saponified with lithium hydroxide monohydrate and dispersed in a California solvent-refined oil, forming a grease having a dropping point of only 324 F.

25.6 grams of the above amic acid (product B) were mixed with 4.4 grams of adipic acid, and this mixture was saponified with lithium hydroxide monohydrate and dispersed in a California solvent-refined oil, forming a grease having a dropping point in excess of 500 F.

Although the grease thickening agents of this invention can be used in lubricating oils in amounts of 6% to 50%, by weight, 10% to 30% are preferred. In the formation of thickened lubricating oils useful for filter oils or for rustproofing agents, less than 6% may be used. That is, in lubricating oils thickened to less than grease consistency,

less than 6% of the thickening agents of this invention can be used.

In addition to the metal soap grease thickening agents of this invention, the grease composition may contain various additives, such as oxidation inhibitors, other thickening agents, gel modifiers, color correctors, extreme pressure agents, etc.

I claim:

1. A grease composition comprising a lubricating oil and a grease thickening agent in an amount sufiicient to thicken said lubricating oil to the consistency of a grease, said thickening agent being prepared by reacting adipic acid with an amine containing from 12 to 18 carbon atoms, wherein the mol ratio of adipic acid to amine has a value from 1.5 to 5, then neutralizing the resulting adipic acidamic acid mixture with an alkali metal hydroxide.

2. A grease composition comprising a lubricating oil and from 6% to 50%, by weight, of a grease thickening agent obtained by reacting adipic acid with n-octadecylamine, wherein the mol ratio of said adipic acid to said n-octadecylamine has a value from 1.5 to 5, forming a metal salt of said adipic acid-n-octadecyladipamate mixture by neutralizing said mixture with an alkali metal hydroxide.

3. A grease composition comprising a lubricating oil and from 6% 'to 50%, by weight, of a grease thickening agent obtained by reacting sebacic acid with n-octadecylamine, wherein the mol ratio of said sebacic acid to said noctadecylamine has a value from 1.5 to 5, forming a metal salt of said sebacic acid-n-octadecyl sebacamate mixture 8 by neutralizing said mixture with an alkali metal hydroxide. v

4. A grease composition comprising a major proportion of a lubricating oil and a grease thickening agent in an amount sufficient to thicken said lubricating oil to the consistency of a grease, said thickening agent being obtained by reacting sebacic acid with an amine containing from 12 to 18 carbon atoms, wherein the mol ratio of sebacic acid to amine has a value of 1.5 to 5, neutralizing the resulting sebacic acid-antic acid mixture with an alkali metal hydroxide.

5. A grease composition comprising a lubricating oil and a grease thickening agent in an amount sufi'icient to thicken said lubricating oil to the consistency of a grease, said thickening agent being prepared by reacting a dibasic acid containing from 410 carbon atoms with an amine containing from 12-8 carbon atoms, wherein the mol ratio of dibasic acid to amine has a value from 1.5 to 5, then neutralizing the resulting dibasic acid-amic acid mixture with an alkali metal hydroxide.

6. The grease composition of claim 5 wherein the two carboxyl groups of said dibasic acid are attached as terminal groups to a polymethylcne radical.

References Cited in the file of this patent UNITED STATES PATENTS 1,937,463 Nill Nov. 28, 1933 2,495,651 Butcosk Jan. 24, 1950 2,594,286 Bryant et al Apr. 29, 1952 2,604,449 Bryant et al July 22, 1952 

5. A GREASE COMPOSITION COMPRISING A LUBRICATING OIL AND A GREASE THICKENING AGENT IN AN AMOUNT SUFFICIENT TO THICKEN SAID LUBRICATING OIL TO THE CONSISTENCY OF A GREASE, SAID THICKNEING AGENT BEING PREPARED BY REACTING A DIBASIC ACID CONTAINING FROM 4-10 CARBON ATOMS WITH AN AMINE CONTAINING FROM 12-8 CARBON ATOMS, WHEREIN THE MOL RATIO OF DIBASIC ACID TO AMINE HAS A VALUE FROM 1.5 TO 5, THEN NEUTRALIZING THE RESULTING DIBASIC ACIDI-AMIC ACID MIXTURE WITH AN ALKALI METAL HYDROXIDE. 